This invention relates in general to plastic forming devices and in particular to a new and useful device for extruding and forming plastic sheets which includes one or more calender rolls over which a sheet is extruded arranged in connection with calender rolls and a smoothing ledge which may be adjustably positioned for forming webs of varying thickness.
The invention relates particularly to an apparatus for processing thermoplastic plastics to material webs, in particular barrier foils for food packaging, with the use of preferably cooled calender rolls, the distance between axles of a pair of feed rolls being adjustable. With such an apparatus, the thermoplastic substance, coming in particular from a sheet die, is rolled to material webs preferably with cooling. The number and arrangement of additional calender rolls depends on product-related criteria which determine, of course,also the feed roll nip, among other things.
A special problem in this connection is that the thickness range of the material webs that can be produced cannot be less than about 600 .mu.m as a lower limit, particularly when the calender rolls are to process webs of up to 12 mm and more. It is a generally known problem to produce especially thin foils in uniform thickness and for this purpose special devices have been developed.